Speckle Free Laser Probe Beam

摘要

A speckle free laser probe beam is desirable for applications where a laser probe beam is preferred but laser speckles are troublesome. For example, it is an ideal replacement of laser or SLD probe beam for ophthalmic wavefront instrument that employs a Hartmann-Shack wavefront sensor. The speckle free laser probe beam employs a rotating disk of holographic phase plate in a laser probe beam path to modify the relative phase across the beam and to randomize the modified relative phase rapidly in a time sequence. The holographic phase plate is designed to produce a small but well-defined diffused angle such that the beam quality of the modified probe beam can remain close to diffraction limit. Our experiment shows that spot image with such a modified laser probe beam is substantially free of speckles. Design considerations and parameters, as well as potential applications, of the speckle free laser probe beam are presented.